A dentinal phosphoprotein found in the teeth of several species, has been implicated in the mineralization process of this tissue. The purified protein is comprised of about 50 percent phosphoserine and 33 percent aspartic acid. Such a polyanionic substance presents insurmountable difficulties in certan physical and chemical approaches to studying its structure. Therefore the phosphate will be removed by alkaline elimination, and the seryl residues converted to alanine by borohydride reduction. Molecular weight and primary structural studies will then be applied. Calcium binding studies will be applied to the natural and to the dephosphorylated protein. Finally, studies on the mechanism of attachment of phosphate to serine hydroxyls, catalyzed by kinases in the odontoblasts, will be initiated.